[MNAPRS] APRS issue in western MN

Sat Mar 29 09:16:26 CDT 2014

I was kind of wondering if QXM is actually at his regular site or not.
It would give the same report sitting on a workbench. I have no way to
determine if QXM is repeating any other packets which would indicate
where it currently is. If it isn't repeating any packets then it might
be running into a dummy load.

Two ways to share a site, put up a second antenna or add another
string of cans to a duplexor. I haven't done the cans yet. The
commercial guys do it all the time for sharing sites, but they have
deep pockets. I understand the usual option is to add a series pass
cavity first in the string, followed by notch cavities and maybe
another pass cavity to get enough isolation. A lot depends on all the
radios involved.

A second antenna is the easier option. You might still require a
series pass cavity or two, and possibly a notch on the repeater RX
frequency in the APRS TX to suck out TX noise. Again, a lot depends on
the radios involved. Most ham transceivers are not the best option if
the radios have to co-exist since they are designed to receive
everything in the VHF band. Although since it is all within the 2M
band, the RX selectivity isn't going to be the issue....

On 3/29/14, Keith Lakeman <keith at lakeman.org> wrote:
> Doug,
>
> Thanks for all of the information. I will capture the output of my TNC when
> I get up to the site again.
>
> It appears that QXM is reporting again. The local igate, NG0W-10, is down,
> so QXM is being heard via a new route. I wonder if NG0W-10 might be part of
> my problem too.  With NG0W-10 down, the path to an igate is longer.
> Is WIDE2-1 allowing my packet to be repeated enough times to reach a more
> distant igate?
>
> I have a new antenna for the site. Waiting for the weather to improve. I am
> also considering upgrading my node to an igate, but would rather leverage
> existing igates.
>
> I have spoke to the owner of the local repeater that my node announces. I
> hadn't considered asking to leverage his site for APRS, but it's a great
> site with great coverage.  I'll see if he is receptive of the idea.
>
> Thanks again,
>
> Keith
> kc0zzq
> keith at lakeman.org
>
> On Thursday, March 27, 2014, Doug Reed <n0nas at amsat.org> wrote:
>
>> You are about 55KM from QXM and about 75KM from CBV. That may be some
>> of it right there.
>>
>> According to aprs.fi, you are on the fringe of the CBV coverage
>> area and it hears a LOT of activity from Fergus Falls, Fargo,
>> Detroit Lakes, and all the traffic on I-94 and Hwy 10.
>>
>> You are also on the fringe of the QXM coverage area, and on the far
>> side of I-94 to boot. But QXM only hears about 20% as many packets as
>> CBV so there is a lot better chance you'll be heard.
>>
>> But also remember that aprs.fi only saves and stores the FIRST
>> reception report it receives. If one station has a faster network
>> connection,  it might be heard first more often. And if there are
>> fewer hops to the I-gate, it will be reported more often. But in this
>> case, the aprs.fi data seems to indicate reception by CBV is VERY
>> spotty.....
>>
>> So the problem could be just due to collisions with other packets. It
>> doesn't really sound like a TNC problem, You are running a KPC-3plus,
>> QXM is running an OpenTracker 3, and CBV is running UIDIGI on a TNC-2
>> compatible of some sort. I suppose that CBV could be on a MFJ TNC and
>> maybe the tone decoder needs a slight center freq adjustment? But CBV
>> has the only TNC that has adjustments among the three TNCs. But it is
>> seeing plenty of activity from other stations.
>>
>> But that doesn't explain why CBV repeats packets digied by your
>> station more often than it repeats your station's own beacons..... But
>> does it really?
>>
>> Have you actually captured the text strings from your KPC-3 and then
>> actually attempted to count and compare how many times you beacon and
>> CBV repeats it versus how many times you digi someone elses packet and
>> your packet is the one repeated by CBV? It looks like you beacon once
>> per hour and QXM last heard 18 beacons in 45 hours, with a bias toward
>> hearing the night-time packets rather than daylight. There would be
>> less traffic on the highway in the night.
>>
>> CBV only heard 4 packets in the last 4 days and there is no
>> significant bias toward AM or PM hours. So QXM was hearing maybe 40%
>> of your beacons but CBV is hearing less than 5%.
>>
>> I will frequently capture a couple days of text from my TNC so I have
>> sample activity to look at. If every digi is properly doing no-wait
>> digipeating as they are supposed to, it can be very difficult to
>> figure out how far you are being heard, but with enough data, you can
>> try....  So go through the text capture and count how often ZZQ and
>> CBV appear in the same line of text. This is something you could do
>> with a simple BASIC program. There may even be some existing software
>> for analyzing APRS or packet traffic that might help.
>>
>> Overall, I don't really see any reason CBV should be hearing and
>> digipeating packets that your WIDE1 retransmitted, but not be seeing
>> beacons originating at your station. I guess I'd make one more change
>> to your config just to see what happens. It looks like you are using
>> the proper WIDE2-1 outgoing path on your beacons but CBV doesn't hear
>> you well. So try changing to WIDE1-1,WIDE2-1 for a while and see what
>> happens. The usual rule is that a fixed station shouldn't use WIDE1-1,
>> but perhaps in this case it will improve your chances of being heard.
>> I don't like the idea, but it is worth trying in case one of the
>> stations in Fergus Falls hears you, or maybe KD0NEL.
>>
>> Have you ever done a radio coverage map of your station? You can go
>> over to Radio Mobile Online, create a free account under your
>> callsign, then enter in your station location as a new site. (It is
>> probably best to drill down to your street by zooming and centering
>> the map until you find it.) Be sure to tag it as your home station
>> too, when you save it. Once that is done you can create a coverage map
>> based on your station and antenna parameters. What I usually use is
>> the existing antenna height, gain, coax loss, and TX power. Then
>> configure the mobile as a default quarter-wave on the car roof, 2M
>> height & 1dB gain, with 1 or 2dB coax loss and 1uv receive
>> sensitivity. I use those numbers because they are conservative and
>> will indicate less range than might actually be obtained. .
>>
>> The resulting coverage map will show about how far a mobile should be
>> able to hear your station. The critical part here is that the coverage
>> map will show you how the terrain is effecting your antenna pattern.
>> If there is a ridge in one direction, your coverage will be less in
>> that direction. If you are looking down a river valley, your coverage
>> will be better in that direction.
>>
>> After you get your home coverage map working, you can add the
>> locations of QXM and CBV and run coverage maps based on the info in
>> their beacons. That will show you where you are from their
>> perspective. If you are behind a ridge from CBV but down valley to
>> QXM, that pretty well explains your problem.... It may not prove
>> anything but the coverage maps can be fun to try.
>>
>> One simple config change you can try would be to change your beacon
>> time to 3595 seconds or 3005 seconds, or some similar random
>> difference from exactly 3600 seconds. Perhaps your beacon is happening
>> about the same moment as someone elses beacon? I usually make a small
>> change of 1 to 3 seconds on my beacon times, just to be safe.
>> Actually, why don't you change back to 30 minute beacons, maybe 1798
>> seconds? 30 minute beacons for a fixed station is not excessive and
>> will keep your symbol on the map all the time.
>>
>> Overall, my guess would be that CBV is just much busier and you are
>> farther away from it. If you can throw in a terrain problem, it is
>> likely everything is working as well as can be expected. You might
>> find significant improvement by raising your antenna another 10 feet.
>> But I think what you really need is a nice high WIDEn-n somewhere
>> between Wadena and Alexandria., or preferably in both cities...  :-)
>> You are beaconing out two repeater frequencies. What are your chances
>> of moving your WIDE1-1 to one of those sites?
>>
>> By the way, did you try to contact N0QXM and tell him the digi is down
>> and ask when it will return? He may not know it is down, or possibly
>> it will be a permanent loss..... I don't think his beacon message is
>> in the correct format either, PHG is at the end rather than
>> immediately after the lat-lon.....  I didn't find an email address for
>> him, just a street address, and a white pages phone number.
>>
>> Maybe someone will have some better ideas.....
>>
>> 73, Doug Reed, N0NAS.
>>
>>
>> On 3/27/14, Keith Lakeman <keith at lakeman.org <javascript:;>> wrote:
>> > I'm looking for a little help in diagnosing an inconsistency I'm seeing
>> in
>> > APRS with my digipeater node, KC0ZZQ-5.
>> >
>> > My node is located near Battle Lake MN.  It's been up since last July.
>> >
>> > My nearest digi's are N0CBV-1 - Barnsville,MN and N0QXM-1 - Morris,MN
>> >
>> > N0QXM-1 has been the node that consistently repeating my node's
>> > announcements.  Last weekend that node went down.
>> >
>> > N0CBV-1 very occasionally repeats packets that originate from my node.
>>  It
>> > is very consistent repeating packets that my digi has repeated
>> > orginating
>> > from another node.
>> >
>> > I'm trying to figure out why N0CBV-1 will not consistently repeat
>> > packets
>> > that originate from my node.
>> >
>> > Any ideas on what could cause this would be appreciated.
>> >
>> > thanks,
>> > Keith
>> > kc0zzq
>> > keith at lakeman.org <javascript:;>
>> >
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